They still hire people from engineering and math backgrounds. People who you know have the competence to understand any technical problem you throw at them, at least at a shallow operational level.

The prerequisite is deep mathematical, rational and process-oriented thinking. You can get that lots of ways, but an MBA alone won't give it to you.

I don't disagree with that. If you run a technical company, managers shoudl demonstrate an ability to think and understand technical problems.

I disagree with the notion that the path through management should be through demonstrating your value as an engineer. If a high performing engineer desires a move into management, I think that should certainly be considered, but I have no evidence that top engineers transition into being top managers.

I would certainly argue that it is easier to find engineering-trained people who can become successful businessfolk, than business-trained people who can competently manage tech companies.

Being a successful engineer is evidence that you understand processes and systems very deeply. What remains is interpersonal skill and basic economics. Being a successful business person is evidence of the complement.

Couple this with the observation that it is easier to find people who picked up economics and interpersonal skills without training than it is to find people with deep untrained technical skill, because interactions with other people and decisions about money occur every day so any motivated somebody with a curious disposition may well have been pondering and improving those skills their whole life.

Remember, it's not that every engineer you find will be better rounded, it's just that those magical omnibus people are more likely to be found among the engineering ranks than the business ranks, especially when engineering jobs give a much more reliable salary out of college so that anyone with engineering skill and business skill is incentivized to study the former in school.